important 351m\400 head question
Thread Starter
|
New User
Joined: Mar 2005
Posts: 24
Likes: 0
important 351m\400 head question
ok hear goes my question i am building a 400 for my truck and i now need a set of heads for it hear is where i am confused the heads that i am looking for are the 351m 2barrel heads on this forum i have read all of the time that the 351 c 2 barrel heads and the 351m\400 2 barrel heads are the same thing and the 351c heads will bolt right up and that they are the same but when i call every salavage yard they say that they are different and they will not work and also the machine shop where i had all of my block work done also said that same thing that they are different and the will not work will someone please give me some good info on my situation thankyou very much
Senior User
Joined: Feb 2004
Posts: 258
Likes: 0
From: e-burg
ok from what i understand the cleveland heads and the m-block heads are the exact same. other than the 4bbl heads have bigger valves. but i can't say this for a fact because i have neither seen both sets side by side nor have i tried to do it. but i think ur on the right track. most junkyards really dont know they just sell the parts.
Postmaster
Joined: Aug 2001
Posts: 4,270
Likes: 5
From: Delaware
The early 351C-2V heads are interchangeable with later 351M heads. The only differences that I know of is the presence of a thermactor bump in the exhaust port on the later heads, and 76.2cc combustion chamber volume on the 351C-2V heads and 78.4 on the 351M/400 heads.. This makes the early heads preferable, but grinding out the thermactor bump will help those heads. The valve sizes are the same on all 335 series 2V heads. (2.041I/1.654E). You can also use Aussie heads, but the combustion chamber is only 58cc, and may make your compression ratio too high.
The 351C-4V heads have huge ports and will not mate to any manifold made for a 351M/400 motor. These have larger valves in most years. (2.19I/1.71E). They come in two open chamber sizes (78.4cc, 75.4cc), and two closed chamber sizes (62.8cc, and the very rare Boss version 66.1cc).
The best thing to do with 335 series 2V heads is to increase the size of the intake valves, and do some porting work on the exhaust ports.
What do you plan to use your truck for?
What pistons do you plan to use?
What kind of cam are you planning to use?
All these questions should be answered to determine your static compression ratio, and the head you should use.
The 351C-4V heads have huge ports and will not mate to any manifold made for a 351M/400 motor. These have larger valves in most years. (2.19I/1.71E). They come in two open chamber sizes (78.4cc, 75.4cc), and two closed chamber sizes (62.8cc, and the very rare Boss version 66.1cc).
The best thing to do with 335 series 2V heads is to increase the size of the intake valves, and do some porting work on the exhaust ports.
What do you plan to use your truck for?
What pistons do you plan to use?
What kind of cam are you planning to use?
All these questions should be answered to determine your static compression ratio, and the head you should use.
Freshman User
Joined: Mar 2005
Posts: 39
Likes: 0
From: Washington
I am building a 1977 400 for the same year f250.
I got a pair of heads from a 71 Cleveland. They will bolt straight up and will give me 9.5/1 comp with flat top pistons and mild cam.
I got a pair of heads from a 71 Cleveland. They will bolt straight up and will give me 9.5/1 comp with flat top pistons and mild cam.
Last edited by Torque1st; Mar 16, 2005 at 01:59 PM.
Freshman User
Joined: Mar 2005
Posts: 39
Likes: 0
From: Washington
Sorry, those are 2v heads I forgot to mention that.
The only down fall to the heads from the 71 Cleveland I bought is that they do not have the quench chamber like the Aussie heads, but will still put me in the high 300hp range
The only down fall to the heads from the 71 Cleveland I bought is that they do not have the quench chamber like the Aussie heads, but will still put me in the high 300hp range
Trending Topics
Lead Driver
Joined: Nov 2000
Posts: 6,648
Likes: 352
From: Albuquerque
All 351m/400 and 351c head have the same combution chamber (American) shape and approximate volume. I believe the valve sizing is also always the same.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 6 Best Deals Available on New Fords & Lincolns Right Now
Brett Foote
This Hennessey Takes the Expedition Tremor's Off-Roading Capability to the Next Level
Verdad Gallardo
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Postmaster
Joined: Aug 2001
Posts: 4,270
Likes: 5
From: Delaware
According to Tom Monroe's book all the 2V heads have the same valve size, but the 351C-2V heads have 76.2cc combustion chambers vs 78.4 for the 351M/400 heads.
1971 351C-2V heads (76.2cc) on a 400 motor will produce about 9.1:1 CR with a Badger flattop with 3cc valve relief and 0.0665" deck clearance. This will be slightly higher with an overbore (9.17:1 for +0.030).
1971 351C-2V heads (76.2cc) on a 400 motor will produce about 9.1:1 CR with a Badger flattop with 3cc valve relief and 0.0665" deck clearance. This will be slightly higher with an overbore (9.17:1 for +0.030).
Posting Guru
Joined: Aug 2000
Posts: 2,416
Likes: 4
From: PacNW
Originally Posted by chrisjr2287
ok hear goes my question i am building a 400 for my truck and i now need a set of heads for it hear is where i am confused the heads that i am looking for are the 351m 2barrel heads on this forum i have read all of the time that the 351 c 2 barrel heads and the 351m\400 2 barrel heads are the same thing and the 351c heads will bolt right up and that they are the same but when i call every salavage yard they say that they are different and they will not work and also the machine shop where i had all of my block work done also said that same thing that they are different and the will not work will someone please give me some good info on my situation thankyou very much
There is absolutely no question that 351C 2V heads will bolt on to a 351M/400 block. In fact 90% of the people out there wouldn't be able to tell the difference between a 351C 2V and 351M head if they were both sitting on a bench side by side. I've even seen "professionally" rebuilt engines with 1 351M head and 1 351C 2V head on them.
Thread
Thread Starter
Forum
Replies
Last Post
cruz76
335 Series- 5.8/351M, 6.6/400, 351 Cleveland
16
Oct 19, 2016 05:35 PM